fix: skip DCP fetch wrapper processing for subagent sessions

Author: Tarquinen

lib/fetch-wrapper/index.ts

@@ -28,7 +28,7 @@ export function installFetchWrapper(
     prompts: SynthPrompts
 ): () => void {
     const originalGlobalFetch = globalThis.fetch
-    
+
     const ctx: FetchHandlerContext = {
         state,
         logger,
@@ -39,6 +39,14 @@ export function installFetchWrapper(
     }
 
     globalThis.fetch = async (input: any, init?: any) => {
+        // Skip all DCP processing for subagent sessions
+        if (state.lastSeenSessionId && state.subagentSessions.has(state.lastSeenSessionId)) {
+            logger.debug("fetch-wrapper", "Skipping DCP processing for subagent session", {
+                sessionId: state.lastSeenSessionId.substring(0, 8)
+            })
+            return originalGlobalFetch(input, init)
+        }
+
         if (init?.body && typeof init.body === 'string') {
             try {
                 const body = JSON.parse(init.body)
@@ -74,14 +82,12 @@ export function installFetchWrapper(
                     init.body = JSON.stringify(body)
                 }
             } catch (e) {
-                // Silently ignore parsing errors - pass through to original fetch
             }
         }
 
         return originalGlobalFetch(input, init)
     }
 
-    // Return cleanup function to restore original fetch
     return () => {
         globalThis.fetch = originalGlobalFetch
     }

lib/hooks.ts

@@ -72,6 +72,20 @@ export function createChatParamsHandler(
             providerID = input.message.model.providerID
         }
 
+        // Track the last seen session ID for fetch wrapper correlation
+        state.lastSeenSessionId = sessionId
+
+        // Check if this is a subagent session and track it to skip fetch wrapper processing
+        if (!state.subagentSessions.has(sessionId)) {
+            const isSubagent = await isSubagentSession(client, sessionId)
+            if (isSubagent) {
+                state.subagentSessions.add(sessionId)
+                logger.info("chat.params", "Detected subagent session, will skip DCP processing", {
+                    sessionId: sessionId.substring(0, 8)
+                })
+            }
+        }
+
         // Cache model info for the session
         if (providerID && modelID) {
             state.model.set(sessionId, {

lib/state.ts

@@ -22,6 +22,10 @@ export interface PluginState {
     googleToolCallMapping: Map<string, Map<string, string>>
     /** Set of session IDs that have been restored from disk */
     restoredSessions: Set<string>
+    /** Set of session IDs that are subagents (have a parentID) - used to skip fetch wrapper processing */
+    subagentSessions: Set<string>
+    /** The most recent session ID seen in chat.params - used to correlate fetch requests */
+    lastSeenSessionId: string | null
 }
 
 export interface ToolParameterEntry {
@@ -45,6 +49,8 @@ export function createPluginState(): PluginState {
         model: new Map(),
         googleToolCallMapping: new Map(),
         restoredSessions: new Set(),
+        subagentSessions: new Set(),
+        lastSeenSessionId: null,
     }
 }